Targeted deletion of Wwox reveals a tumor suppressor function

Abstract

The WW domain-containing oxidoreductase (WWOX) spans the second most common fragile site of the human genome, FRA16D, located at 16q23, and its expression is altered in several types of human cancer. We have previously shown that restoration of WWOX expression in cancer cells suppresses tumorigenicity. common fragile site ͉ FHIT ͉ knockout ͉ osteosarcoma ͉ lung cancer T he WW domain-containing oxidoreductase (WWOX) encodes a 46-kDa protein that contains two WW domains and a short-chain dehydrogenase/reductase domain (1-3). The WWOX gene is altered by deletions or translocations in a large fraction of many cancer types including breast, prostate, esophageal, lung, stomach, and pancreatic carcinomas (2, 4-9). WWOX protein is lost or reduced in the majority of these cancers and in a large fraction of other cancer types (10, 11). WWOX spans the second most active common fragile sites, FRA16D (reviewed in ref. 12). Common fragile sites are large regions of profound genomic instability found in all individuals. Following partial inhibition of DNA synthesis, those regions show site-specific gaps or breaks on metaphase chromosomes. In addition, common fragile sites exhibit induction of sister chromatid exchange and show a high rate of translocations and deletions in somatic cell hybrids (13). Because FRA16D maps within regions of frequent loss of heterozygosity, and is associated with homozygous deletions in various adenocarcinomas and with chromosomal translocations in multiple myeloma (2), these rearrangements have been suggested to inactivate the WWOX gene. On the other hand, ectopic overexpression of WWOX in cancer cells lacking expression of endogenous WWOX results in significant growth inhibition and prevents the development of tumors in athymic nude mice (14,15). In addition, we reported that restoration of WWOX expression in cancer cells results in caspase-mediated apoptosis (15). Thus, these data suggest that WWOX may act as a tumor suppressor Biochemical and functional characterization of WWOX has shown that it interacts with proline-tyrosine rich motifcontaining proteins. WWOX associates via its first WW domain with p73 and enhances p73-mediated apoptosis (16). WWOX also binds to the PPPY motif of AP2␥ and ErbB4, established oncogenes in breast cancer (17,18). Interestingly, WWOX suppresses the transcriptional ability of these target proteins by sequestering them in the cytoplasm (16)(17)(18). Taken together, accumulating evidence, both in cell culture and in nude mice, suggests that WWOX functions as a tumor suppressor, although no direct in vivo proof has yet been reported to verify WWOX as a bona fide tumor suppressor. To define the role of WWOX protein in cancer development, we generated mice carrying a targeted deletion of the Wwox gene. The murine Wwox locus is similar to its human homolog (19), spans the Fra8E1 common fragile site, and is highly conserved. Here, we demonstrate that the loss of both alleles of Wwox results in osteosarcomas in some early postnatal mice, whereas loss of one allele signifi...

Wwox inactivation enhances mammary tumorigenesis

“…Mammary tumor incidence in C3H-Wwox mice We previously reported that Wwox þ /À mice on B6-129 mixed background develop higher incidence of lung tumors as compared with Wwox þ / þ mice (Aqeilan et al, 2007c). We also noted that some of these mice develop mammary tumors though with very low penetrance (data not shown).…”

“…Recently, we generated a mouse carrying a targeted deletion of the Wwox gene (Aqeilan et al, 2007c). Spontaneous osteosarcomas were observed in juvenile Wwox-null mice before their death, whereas targeted loss of one allele increased the incidence of spontaneous and chemically induced lung and forestomach tumors (Aqeilan et al, 2007b, c;Kurek et al, 2010) thus confirming Wwox bona fide tumor suppressor function.…”

Inhibition of the Wnt/β-catenin pathway by the WWOX tumor suppressor protein

“…Homozygous deletion of WWOX exons has been found in different cancer cell lines Paige et al, 2000Paige et al, , 2001, and hypermethylation of the WWOX promoter has been detected in both cancer cell lines and primary tumors (Ishii et al, 2003;Kuroki et al, 2004;Iliopoulos et al, 2005). The expression of WWOX is reduced or lost in many different cancers (Aqeilan et al, 2007c). Notably, it has been established that WWOX is inactivated in invasive breast carcinoma (Guler et al, 2004Chang et al, 2005;Nunez et al, 2005;Wang et al, 2009).…”

“…Several tumor types, such as human breast tumors, overexpress aberrant transcripts (Driouch et al, 2002;Ludes-Meyers et al, 2003). Moreover, WWOX has the capacity to function as a tumor suppressor gene both in vitro and in vivo (Bednarek et al, 2001;Kuroki et al, 2004;Fabbri et al, 2005;Iliopoulos et al, 2007;LudesMeyers et al, 2007;Qin et al, 2007;Aqeilan et al, 2007bAqeilan et al, , 2007c. Together, these findings suggest that WWOX is a tumor suppressor gene.…”

The Tumor-Suppressor WWOX and HDAC3 Inhibit the Transcriptional Activity of the β-Catenin Coactivator BCL9-2 in Breast Cancer Cells

“…The decrease of WWOX expression in breast cancer is associated with a poor clinical outcome for patients (3,4). Although WWOX ectopic expression inhibits tumor growth in different cell types in vitro and in vivo, the targeted ablation of the murine WWOX gene leads to carcinoma (5). Moreover, the incidence of tumor formation in WWOX þ/À mice is significantly higher than in WWOX þ/þ mice.…”